Liquid crystal display devices have conventionally been used for desk calculators, electronic clocks, personal computers, etc. and in recent years there is an increasing demand therefor, and recently they are also applied to a wide range of applications such as mobile phones, tablet type terminals and the like. These liquid crystal display devices normally include as a main member a liquid crystal display panel including a liquid crystal cell with a pair of polarizing plates that are disposed on front and back sides of the liquid crystal cell.
In the recent market, as mobile devices such as mobile phones and tablet type terminals having a screen increased in size are widely used, there is a demand for reduction in weight and thickness of a constituent member thereof, namely a liquid crystal display panel, and there is a tendency to reduce a liquid crystal cell's glass substrate, a front plate and/or the like in thickness. Furthermore, in order to eliminate reflection and scattering of light at an interface to enhance visibility, there is also a tendency to integrate the front plate with the liquid crystal display panel using a pressure sensitive adhesive, an ultraviolet curing type resin or the like.
Conventional liquid crystal display panels have a thick front plate and a thick liquid crystal cell, and their warping resulting from a polarizing plate's shrinkage has thus been suppressed even in high temperature environments. The above-mentioned recent tendency to reduce in thickness the front plate, the glass substrate used for a liquid crystal cell and the like, however, results in the warping of the liquid crystal display panel, which is attributed to the polarizing plates shrinkage in high temperature environments, and as a consequence, for example, a problem has arisen that the liquid crystal display panel cannot be accommodated in a casing for a final product.
In order to suppress such warping of the liquid crystal display panel, a conventionally known methodology provides a polarizing plate (a front-side polarizing plate) to be disposed at a viewing side of a liquid crystal cell and a polarizing plate (a back-side polarizing plate) to be disposed at a side opposite to the viewing side of the liquid crystal cell (a back-side) such that the polarizing plates are different in thickness. For example, Japanese Patent Laying-Open No. 2012-058429 (PTD 1) describes a method for suppressing a liquid crystal display panel's warping by reducing a front-side polarizing plate's polarizing film (polarizer) to be smaller in thickness than a back-side polarizing plate's polarizing film.
However, a liquid crystal display panel's warping in a high temperature environment is attributed to a polarizing plate's shrinkage that depends upon a polarizer's thickness, as has been set forth above, and when the polarizer of the front-side polarizing plate is reduced in thickness, as described in PTD 1, a liquid crystal display panel having a front plate integrated using a pressure sensitive adhesive or an ultraviolet curing type resin for improved visibility, in particular, may have the warping, and suppression of the warping is thus not necessarily satisfactory.
Furthermore, Japanese Patent Laying-Open No. 2002-221715 (PTD 2) describes that in a liquid crystal display element (a liquid crystal display panel) using a plastic-substrate-containing liquid crystal cell, a protective layer that constitutes a front-side polarizing plate is smaller in thickness than a protective layer that constitutes a back-side polarizing plate to suppress the amount of warping of the plastic-substrate-containing liquid crystal cell. When the method making protective layers different in thickness, as described in PTD 2, is applied to a liquid crystal display panel having a front-side polarizing plate with a front plate integrated therewith for improved visibility, however, a liquid crystal cell of the panel may have the warping resulting from the protective layer's thermal shrinkage and the problem may arise that the panel cannot be accommodated in a casing for a final product.